1. Field of the Invention
The present invention relates to an electronic musical instrument which employs a frequency number corresponding to a fundamental frequency of each key and is capable of producing a natural and expressive effect such as vibrato or the like with a simple structure.
2. Description of the Prior Art
Usually, a violin, viola, cello or like instrument is played with vibrato. In relation to the playing speed, what is called a delayed vibrato technique is used which starts with slight vibrato of low speed and gradually develops fast and deep vibrato. Electronic musical instruments for producing such an effect are known from Japanese Laid-Open Patent Gazettes Nos. 132327/78 and 115127/79. According to these prior art examples, in an electronic musical instrument which employs frequency numbers, a fractional frequency number is obtained from a frequency number based on produced frequency modulated data and it is added to or subtracted from its original frequency number, to obtain a frequency modulated number corresponding to the produced frequency modulated data. Accordingly, the prior art electronic musical instruments require a multiplier for obtaining the fractional frequency number, a complementor for converting the multiplier output into a complement and an adder for adding the complementor output and the original frequency number. The conventional circuit arrangement involves many adders, and hence it is complex. The present invention is intended to produce the same effect as described above by using highly reliable, large-capacity and small fixed memories (ROMs) in place of the aforementioned multipliers and adders.